1 files changed, 210 insertions, 0 deletions
diff --git a/back-end/src/FeedGenerator.cs b/back-end/src/FeedGenerator.cs
new file mode 100644
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+/*
+* Copyright (c) 2023 Vaughn Nugent
+* 
+* Library: CMNext
+* Package: Content.Publishing.Blog.Admin
+* File: FeedGenerator.cs 
+*
+* CMNext is free software: you can redistribute it and/or modify 
+* it under the terms of the GNU Affero General Public License as 
+* published by the Free Software Foundation, either version 3 of the
+* License, or (at your option) any later version.
+*
+* CMNext is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+* GNU Affero General Public License for more details.
+*
+* You should have received a copy of the GNU Affero General Public License
+* along with this program. If not, see https://www.gnu.org/licenses/.
+*/
+
+using System;
+using System.Xml;
+using System.Linq;
+using System.Text;
+using System.Collections.Generic;
+
+using VNLib.Utils.IO;
+using VNLib.Plugins;
+
+using Content.Publishing.Blog.Admin.Model;
+
+namespace Content.Publishing.Blog.Admin
+{
+    internal sealed class FeedGenerator : IRssFeedGenerator
+    {
+        const int defaultMaxItems = 20;
+        const string ITUNES_XML_ATTR = "http://www.itunes.com/dtds/podcast-1.0.dtd";
+        const string CONTENT_XML_ATTR = "http://purl.org/rss/1.0/modules/content/";
+
+        public FeedGenerator(PluginBase pbase)
+        { }
+
+        public void BuildFeed(IChannelContext context, IEnumerable<PostMeta> posts, VnMemoryStream output)
+        {
+            _ = context.Feed ?? throw new ArgumentNullException(nameof(context.Feed));
+
+            //Build the feed
+            using XmlWriter writer = XmlWriter.Create(output, new XmlWriterSettings
+            {
+                Encoding = Encoding.UTF8,
+                Indent = true,
+                IndentChars = "  ",
+                NewLineChars = "\n",
+                NewLineHandling = NewLineHandling.Entitize,
+                NewLineOnAttributes = false,
+                CloseOutput = false,
+                NamespaceHandling = NamespaceHandling.OmitDuplicates,
+            });
+
+            string currentTime = DateTime.UtcNow.ToString("R");
+
+            //Write the feed
+            writer.WriteStartDocument();
+            writer.WriteStartElement("rss");
+            writer.WriteAttributeString("version", "2.0");
+            writer.WriteAttributeString("xmlns", "itunes", null, ITUNES_XML_ATTR);
+            writer.WriteAttributeString("xmlns", "content", null, CONTENT_XML_ATTR);
+          
+
+            //Channel element
+            writer.WriteStartElement("channel");
+
+            writer.WriteElementString("title", context.BlogName);
+
+            writer.WriteElementString("link", context.Feed.PublihUrl);
+
+            //Description/summary
+            writer.WriteElementString("description", context.Feed.Description);
+            writer.WriteElementString("itunes", "summary", null, context.Feed.Description);
+
+            writer.WriteElementString("itunes", "author", null, context.Feed.Author);
+
+            //Itunes owner tag
+            writer.WriteStartElement("itunes", "owner", null);
+            writer.WriteElementString("itunes", "email", null, context.Feed.WebMaster);
+            writer.WriteElementString("itunes", "name", null, context.Feed.Author);
+            writer.WriteEndElement();
+
+            //Write extended properties 
+            if (context.Feed.ExtendedProperties != null)
+            {
+                foreach (ExtendedProperty prop in context.Feed.ExtendedProperties)
+                {
+                    PrintExtendedProps(prop, writer);
+                }
+            }
+
+            //Author
+            writer.WriteElementString("itunes", "author", null, context.Feed.Author);
+
+            //Itunes image url
+            if (context.Feed.ImageUrl != null)
+            {
+                WriteImageTag(writer, context.Feed.ImageUrl);
+            }
+
+            writer.WriteElementString("language", "en-us");
+
+            writer.WriteElementString("pubDate", currentTime);
+            writer.WriteElementString("lastBuildDate", currentTime);
+
+            int maxItems = context.Feed.MaxItems ?? defaultMaxItems;
+            //Take only the latest max items
+            posts = posts.OrderByDescending(static p => p.Date).Take(maxItems);
+
+            //Write the posts as items but sort in order of their pub date
+            foreach (PostMeta post in posts)
+            {
+                writer.WriteStartElement("item");
+
+                writer.WriteElementString("title", post.Title);
+                writer.WriteElementString("itunes","title", null, post.Title);
+
+                writer.WriteElementString("link", $"{context.Feed.PublihUrl}/{post.Id}");
+               
+                writer.WriteElementString("itunes", "author", null, post.Author);
+
+                //Description is just the post summary
+                writer.WriteElementString("description", post.Summary);
+                writer.WriteElementString("itunes", "summary", null, post.Summary);
+
+                //Time as iso string from unix seconds timestamp
+                string pubDate = DateTimeOffset.FromUnixTimeSeconds(post.Date).ToString("R");
+
+                writer.WriteElementString("pubDate", pubDate);
+                writer.WriteElementString("published", pubDate);
+
+                if (post.Image != null)
+                {
+                    WriteImageTag(writer, post.Image);
+                }
+
+                //Add extended properties as itunes tags
+                if (post.ExtendedProperties != null)
+                {
+                    //Recursivley add extended properties
+                    foreach (ExtendedProperty prop in post.ExtendedProperties)
+                    {
+                        PrintExtendedProps(prop, writer);
+                    }
+                }
+
+                //Set post id as the guid
+                writer.WriteElementString("guid", post.Id);
+
+                writer.WriteEndElement();
+            }
+
+            //End the feed
+            writer.WriteEndElement();
+            writer.WriteEndElement();
+            writer.WriteEndDocument();
+        }
+
+        private static void PrintExtendedProps(ExtendedProperty? prop, XmlWriter writer)
+        {
+            if (prop?.Name == null)
+            {
+                return;
+            }
+
+            //Open the element
+            writer.WriteStartElement(prop.NameSpace, prop.Name, null);
+
+            //Write the attributes
+            if (prop.Attributes != null)
+            {
+                foreach (KeyValuePair<string, string> attr in prop.Attributes)
+                {
+                    writer.WriteAttributeString(attr.Key, attr.Value);
+                }
+            }
+
+            //nested child elements before closing
+            if (prop.Children != null)
+            {
+                foreach (ExtendedProperty child in prop.Children)
+                {
+                    PrintExtendedProps(child, writer);
+                }
+            }
+            else
+            {
+                //Write the value
+                writer.WriteString(prop.Value);
+            }
+            
+            //Close the element 
+            writer.WriteEndElement();
+        }
+
+        private static void WriteImageTag(XmlWriter writer, string imageUrl)
+        {
+            writer.WriteStartElement("itunes", "image",null);
+            writer.WriteAttributeString("href", imageUrl);
+            writer.WriteEndElement();
+        }
+    }
+}